SANDBOX MODE

[GMG]

will there ever be a sandbox mode with no cost building and no damage?

[NoOblet]

you can always use console commands until there is =)

[Ich Weiß Nichts]

Yep, use freedom mode, then use the cheat console (F3, uncheck disable console, use tilde ~ key to bring it up). The cheats you'll need, without quotes are "nocost" "nodamage" "oxygen". This will allow anything to be constructed, without having the materials, it will turn off player damage, and keep you from needing oxygen. I know this may not be the answer you were looking for, but it'll work for what you're wanting to do.